Transcript PAIN MANAGEMENT - delhisurgery / FrontPage

Pain Management
Why Treat Pain?
Animals feel pain just like us
 Unethical not to address pain
 Animal owner and public concerns
 Many anesthetics have no analgesic effect
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– Which do?
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Pain results in poor anesthetic recovery
MYTHS
“Anesthetics mask symptoms”
“Patient will harm itself if there’s
no pain”
“Pain is difficult to assess”
The Truth!
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Pain is BAD:
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Decreased cardiovascular function
Decresed appetite
Slows wound healing
Decreased immune function
» Greater chance of infection
– Increased fear and anxiety
Use of Analgesics in Practice
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Overall = poor
– 13-26% dog and cat spay/neuters receive analgesics
– 50-70% of non-neutering soft tissue surgery
– >80% orthopedic surgery and severe trauma
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Why not better?
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DEA / theft concerns
Older vets not trained that way
Older drugs dangerous
Animals are stoic
Pain Perception
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Pain sensor nerve fiberspinal cordbrain
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Neurotransmitters>>
– Somatic ( superficial ) pain
– Visceral ( internal organ ) pain
– Bone pain
Classification of Pain
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Intensity (scale of 1-10)
Acute, sharp, sudden, short
– Surgical pain
– Responds well to drug tx
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Chronic, dull, prolonged
– Cancer or arthritis
– Doesn’t always respond well to tx
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Referred (from somewhere else)
Hyperesthesia (increased sensitivity)
Neuropathic (Nerve damage)
– Poorly responsive
Degree and Type of Pain Depend On
The procedure
 The animal
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– Pain is an individual experience
» Tailor analgesic protocol to the patient
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Analgesic administration
– Timing
– Dosage
Preemptive Analgesia
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If the body doesn’t sense the pain
during the procedure, the pain will be
easier to deal with post-operatively
– A patient in surgical anesthesia is not
aware of pain, but the body is still
responding sensitizes the nervous
system
Preemptive Analgesia Results In
Marked decrease in amount of analgesic
medication needed post-operatively
 Increased patient comfort
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Balanced Anesthesia
Several anesthetic drugs are combined
into anesthetic protocol
 Include analgesic
 Synergism
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– Smaller dosages needed
– Decreased potential for side effects
Monitoring Signs of Pain
Facial Expression
Vocalization
Body Posture
Abnormal Gait
Decreased Activity Level
Attitude
Appetite
Grooming
Urination/Defecation Habits
Methods of Pain Control
 Non-pharmacological
methods:
Endorphins = The body’s natural painkillers
 Good nursing care
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– Comfortable bedding
» Clean and dry
– Easy access to bathroom, food, water
– TLC
– Rotate recumbency
– Allow time to sleep
Non-pharmacological Methods
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Apply cold to site (acute- 1st 24 hours)
– Decreases inflammation
– Numbs
Apply heat to site (chronic)
 Massage
 Acupuncture/acupressure
 Complementary methods
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– Herbs, laser, magnetic, chiropractic
Pharmacologic Methods
Opioids
 2 agonists
 Steroids
 NSAIDS
 Local anesthetics
 Chondroprotective drugs
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Opioids
Opiate Receptors
MOA?
4 types of receptors:
mu
kappa
sigma
delta
Should we be wondering why fraternities/sororities
name themselves after receptors of pain??
Opioids:
Backbone of Analgesia
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Pure Agonists
– Morphine, oxymorphone, meperidine, hydromorphone,
fentanyl
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Partial agonists, mixed agonist-antagonists
– Buprenorphine
– Butorphanol
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Pure Antagonists (reversal of agonists)
– Naloxone
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ABUSE POTENTIAL
Opioid Administration
Systemic: IV, SQ, IM, CRI
 Intra-articular injection
 Local injection
 Epidural injection
 Transdermal fentanyl patch
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Opioid Effects
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GOOD:
– Great analgesia
– Variable muscle relaxation
– Sedation
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BAD:
– Respiratory depression
– GI effects
» Vomiting
» Defecation followed by constipation
Opioids (other effects)
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Excitement
– Panting
– Vocalization
– Noise sensitivity
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Depression of the cough center
– Advantage for?
Fentanyl Patch
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Lag time:
– apply 6-12 hours prior to surgery in cats,
– 12-24 hours in dogs
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Lasts about 3 days (up to 6 in cats)
Variation in absorption rate
– Dose of patch (in micrograms/hr)
– Avoid heat sources
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Excessive amounts can cause ataxia,
sedation in dogs, excitement, disorientation,
wide-eyed stare in cats
– Remove patch, can reverse
Fentanyl Patch
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Applied to dorsal neck or
shoulders, lateral thorax
Clip hair, clean skin with
water only
Do not cut patch
– Can remove just part of
backing if small animal
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Apply patch, hold firmly 2
minutes
Bandage
Opioid Partial Agonists
Buprenorphine
 Buprenex®
 4-8 hour duration
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Opioid Mixed Agonist-Antagonist
Butorphanol
 (Torbutrol®, Torbugesic®)
 For mild to moderate pain
 Duration 1 to 4 hours IM, SQ
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Less abuse potential than agonists
Opioid Antagonists
 Naloxone
Used to reverse opiates/opioids
 Remember: Reverses analgesia too!
 May not last as long as the agonist
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– Relapse =“renarcotization”
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Partial reversal with butorphanol possible
Alpha-2 Agonists
“thiazines”
Alpha-2 Agonists
 MOA?
Engages receptors in CNS >> decrease norepinephrine
 Examples:
–Xylazine (Rompun®)
–Medetomidine (Domitor®)
Xylazine: Good Things
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Moderate analgesia
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Potent sedative effect
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Good muscle relaxation
Xylazine: Bad Things
Bradycardia due to stimulation of the
vagus nerveheart block
 Profound cardiac disturbances!
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– Sensitizes the heart to
catecholaminesArrhythmias
– Decreased cardiac output
» Hypotension (BP decreases by 1/4-1/3)
Xylazine: More Bad Things
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Vomiting (sometimes used as emetic)
Xylazine: Reversal?
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Yohimbine is reversal agent
Mixed Alpha- antagonist (blocker)
 Trade name “Yobine”
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Medetomidine
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=DOMITOR®
More specific to
CNS alpha-2
receptors
Alpha-2 so has
reversal agent
– (Antisedan®)
Steroids= corticosteroids,glucocoticoids
• Examples:
– Prednisone = Prednisolone
– Dexamethasone
– Betamethasone
– Solu-Delta-Cortef
– Solu-Medrol
• Decrease pain
by decreasing inflammation
Steroids: MOA
inhibit phospholipase A2>>>
inhibits prostoglandin/leukotrienes
Membrane Phospholipid
Phospholipase A2
Steroids
inhibit here
Arachidonic Acid
COX-2
NSAIDS inhibit here
“Bad” Prostaglandins
Pain/Inflammation
COX-1
Thromboxane
“Platelets”
“Good” Prostaglandins
GI Protection
Renal Blood Flow
Side Effects and Toxicity
• Iatrogenic hyperadrenocorticism
– “Cushings Dz”
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Polyphagia
PU/PD
Glaucoma and cataracts
Gastric ulceration
Delayed wound healing
Immunosuppression
More !
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Insulin resistance
Hepatopathy
CNS: restlessness, seizure activity
Infection
Non-Steroidal Anti-inflammatory
Drugs ( NSAIDS )
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Aspirin
Carprofen - Rimadyl ®
Etodolac - Etogesic®
Ketoprofen - Ketofen ®
Phenylbutazone – “Bute”
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Flunixin - Banamine ®
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(Acetaminophen - Tylenol ®)
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NSAIDS
Most have effective somatic (superficial)
analgesic effect
 Some have good visceral analgesic effect also
 All take 30-60 minutes to take effect, even if
injected
 All have antiinflammatory properties
 Reduce fevers
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NSAIDS
MOA: cyclooxygenase inhibitors >>
prostaglandin inhibitors
 Many side effects are due to “good”
prostaglandin inhibition (COX 1):
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– GI upset/ ulceration
– Renal toxicity
– Impaired platelet function
NSAIDS: MOA
inhibit cyclooxygenase>>>
inhibits prostoglandin/thromboxane
Membrane Phospholipid
Phospholipase A2 Steroids
inhibit here
Arachidonic Acid
COX-2
NSAIDS inhibit here
“Bad” Prostaglandins
Pain/Inflammation
COX-1
Thromboxane
“Platelets”
Fever
“Good” Prostaglandins
GI Protection
Renal Blood Flow
NSAIDS - Metabolism
Metabolized by the liver
 Variation in metabolism between species
 Aspirin half-life 12 hours in dogs, 1 hour in
horses, 38 hours in cats
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Many NSAIDS toxic to cats due to inability
to metabolize them
 Acetaminophen is toxic in dogs AND cats!
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NSAIDS Inhibit Production of
Protective GI Prostaglandins
Erosion/ulceration of GI tract
 Stomach upset
 Inappetance
 Vomiting
 Diarrhea
 Melena ?
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Prostaglandins in the Kidneys
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Cause dilation of renal vasculature, allowing
perfusion despite decreased blood pressure
due to
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Shock
Dehydration
Blood loss
Anesthesia
Inhibition of prostaglandin production can cause
kidney cell death due to lack of perfusion
Only an issue if decreased BP
NSAIDS
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Cyclooxygenase
inhibition
decreased
thromboxane
decreases platelet
adhesion/clumping
decreases clot
formation and
thromboemboli
TYPES of NSAIDs
Phenylbutazone
COX1 and 2 Inhibitor
 Very Potent
 Commonly used in horses
 Not recommended in dogs
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– GI side effects common
– NEVER IN CATS!
Aspirin
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COX1 and 2 Inhibitor
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Very short half-life in horses
Commonly used in dogs
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– Buffered only
– With food
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Use with caution in cats
– Can’t metabolize well
– Half-life 38 hours
– Dosed every 48-72 hours
Ibuprofen = “Advil”
COX1 + COX2 Inhibitors
Officially not recommended in
dogs.
most do OK if used like aspirin
Neither Ibuprofen Nor
Naproxen Is Recommended
Ketoprofen
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Ketofen® (COX1 and COX2)
Licensed in horses
Approved for use in dogs and cats in
Canada, Europe
Good analgesia, potent antipyretic
Injectable
– Limit use
– Blood clotting
Flunixin meglumine
Banamine® (COX1 and COX2)
 Injectable
 Horses
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– Colic
– Good analgesia
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Dogs
– GI side effects common, severe
Carprofen
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Rimadyl ®
COX-2 inhibitor: “spares”
“good” prostaglandins
Fewer side effects
DOGS ONLY
Black labs…
– 0.06% of all dogs develop
hepatic problems (rare)
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BID Dosing
Etodolac
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Etogesic ®
COX 1 and 2 Inhibition
Once daily administration
DOGS ONLY
Derramax
Use in dogs
 COX 2 Specific
 SID dosing
 $$
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“Metacam” =Meloxicam
COX-2 Specific
 Use in dogs and cats
 Liquid
 Well tolerated
 $$
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NSAID Precautions
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Use only 1 NSAID at a time
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Never combine NSAIDS with glucocorticoids
– Gastric Ulceration
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Taper to lowest effective dose
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Change to alternative NSAID if poor response
NSAID Contraindications
Renal of hepatic dysfunction
 Decreased circulating blood volume
 Coagulopathies
 GI disease
 Pregnancy
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Local Anesthetics
Local Anesthetics
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The “-caine” family: Lidocaine,
bupivicaine, mepivicaine,
proparicaine, tetracaine, etc.
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MOA= Block nerve impulses by
blocking Na+ channels in nerve
membranes
Local Anesthetics
Local infiltration of surgical site
 Intravenous regional anesthesia
 Intra-articular injection
 Nerve blocks
 Epidural
 Topical on skin/ eye/ larynx
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http://www.cvm.okstate.edu/courses/vmed5412/Lect23.asp
Commonly Used With
Neuroleptanalgesic
Capsaicin
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Hot peppers
Excites then fatigues nerve
transmissionlocal
analgesia
Also get endorphin release
St. Johnswort
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Arthritic pain
Hypericin
– Stimulates neural
inhibitory pathways
analgesia
Chondroprotective Agents
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Nutraceuticals
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Chondroitin sulfate
Glucosamine
Hyaluronic acid
Building blocks for
cartilage and
synovial fluid
Examples: (oral) Synovi, Glycoflex (injectable) Adequan
Can be mixed with many other ingredients
(MSM, Creatine) to enhance effects.
Antibiotic Analogy
to understand pain control
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Antibiotics prescribed based on clinical signs, not
always based on culture and sensitivity
Rely on return to normal function to confirm diagnosis
If doesn’t help, add to or change drug protocol
May need a loading dose
May need a combination of drugs
Questions??